As far as I remember, the author wanted to check the security (how safe is bitcoin), And a few years ago, the author "opened" the public keys for testing the kangaroo. It is possible that the authors are https://fr.wikipedia.org/wiki/National_Security_Agency  

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As I understand it, gpu does not speed up the program code itself, but allows you to run more programs due to more processors. Therefore, the weak link is directly converting a digit to an address and its comparison. Can generate numbers in trillions without gpu.